Even today the power chord is the bedrock of metal guitar and rightfully so--it's basic makeup is the pulverizing interval of a fifth. Drenched in harmonically rich overdive and fueled by some neighbor [dis]approved decibel levels, the sound of a root-fifth chord will even get grandma throwing up a devil horn. But, did you know there exists another powerful sounding interval that will aptly bring the rain? Enter the perfect fourth. The inverted alter-ego to the perfect fifth, the interval of a fourth was the fuel behind such legendary firestorms as Deep Purple's "Burn" and the ultimate 'must-know' riff, "Smoke on the Water". Let's combine the two over an onslaught of modern double bass mania.